Your problem perhaps may be that you rely mostly on sci-fi

The problems I have with the story come entirely from the grammar. I could not figure out the act to which the term "this act" referred. Your wording implies that it refers to the impregnation.

[The Wikipedia page](https://en.wikipedia.org/wiki/Tenet_(film) for the movie Tenet) talks about a reverse-entropy bullet that can travel back in time. So it is possible that the protagonist fired an reverse-entropy bullet that killed someone two generations previously.

But the firing of the reverse entropy bulltet could not be the act because firing a bullet does not bring a person into existence.

The term "exist," which you use several times, has hundreds of complex philosophical connotations which I cannot possibly address.

Anyway, the act that brought the protagonist into existance must be the impregnation to which you referred to in the last sentence.

I can't wait to see your explanation. I am pretty sure that it does not fit the clues given